Theme 5. Igneous rocks - Jurnalul lui Ştefan · Theme 5. Igneous rocks 5.1. Igneous rocks and plate tectonics 5.2. Igneous structures and forms 5.3. ... T.H. Jordan, F. Press, R

Theme 5.

Igneous rocks

5.1. Igneous rocks and plate tectonics

5.2. Igneous structures and forms

5.3. Classification of igneous rocks


Remember!

The lithosphere is underlain by a plastic layer of the

mantle, the asthenosphere, over which the plates

can move.

Source: Understanding Earth – J.Grotzinger, T.H. Jordan, F. Press, R. Siever


Remember!

The theory of plate tectonics describes:

-the movement of plates;

-the forces acting between them.

The theory of plate tectonics explains:The theory of plate tectonics explains:

-continental drift;

-volcanoes;

-earthquakes;

-the distribution of mountain chains;

-rock assemblages;

-structures on the seafloor.


Remember!

Source: USGS


There are two major magmatic geosystems:

-mid-ocean ridges (where basalt wells up from the

upper mantle and melts during decompression to

form oceanic crust);form oceanic crust);

-subduction zones (where subducting oceanic

lithosphere partially melts by addition of fluid to

generate differentiated magmas that rise through

the crust and form island or continental volcanic

arcs).


Source: Understanding Earth – J.Grotzinger,

T.H. Jordan, F. Press, R. Siever

Mid-ocean ridges

(magmatic geosystem)


Mid-ocean ridges



5.1. Igneous rocks and plate tectonicsMid-ocean ridges




Mid-ocean ridges





Mid-ocean ridges



Source: Understanding Earth –

J.Grotzinger, T.H. Jordan, F. Press,

R. Siever

Subduction zones





R. Siever

Subduction zones





R. Siever

Subduction zones



Subduction zones



J.Grotzinger, T.H. Jordan, F.

Press, R. Siever





R. Siever

Subduction zones



Basic extrusive and intrusive structures are:

-volcanic cone;

-ash falls and pyroclastic rock;

-lava flow;

-volcanic neck;

Extrusive structures

-volcanic neck;

-batholith;

-stock;

-dyke;

-sill;

-mineral vein.

Intrusive structures


Plutons are large


J.Grotzinger, T.H. Jordan, F. Press, R. Siever

Plutons are large

igneous bodies

formed at depth

in Earth's crust.


Volcanic cones mark the magma duct or vent.

These are composed of layers of ash and lava, and they

vary in the steepness of their sides according to the

composition of the lava and the amount of ash and dust

ejected.

Source: Internet


The ash and dust ejected from volcanoes is

pyroclastic rock.

The dust and fine ash may settle on land or in

water to form tuffs.

Source: Internet


Volcanic neck

Lava flow

Volcanic neck

Source: Internet





Plutons are large igneous bodies formed at depth in

Earth's crust.

They range in size from 1 km3 to hundreds of km3.

Batholiths, the largest plutons, are great irregular masses

of coarse-grained igneous rock that by definition cover atof coarse-grained igneous rock that by definition cover at

least 100 km2.

Batholiths are found in the cores of tectonically

deformed mountain belts.

The rest of the plutons, similar but smaller, are called

stocks.


Batholiths

and

stocks

Source: Internet





Sills and dikes are similar to plutons, but they are smaller

and have a different relationship to the layering of the

surrounding intruded rock.

A sill is a sheetlike body formed by the injection of magma

between parallel layers of preexisting bedded rock.between parallel layers of preexisting bedded rock.

Sills are concordant intrusions.

Dikes are the major route of magma transport in the

crust. They are like sills in being sheetlike igneous bodies,

but dikes cut across layers of bedding in country rock and

so are discordant intrusions.



J.Grotzinger, T.H. Jordan, F.

Press, R. Siever


Mineral veins are deposits of

minerals found within a rock

fracture that are foreign to the

host rock.

Irregular pencil-shaped or sheet-

shaped veins branch off the tops

and sides of many intrusiveand sides of many intrusive

bodies.

They may be a few millimeters to

several meters across, and they

tend to be tens of meters to

kilometers long or wide.

Mineral veins can contain

economic metals or gems.Source: Internet

Minerals

(Chemical bonds, Crystals)

RocksWholeness

God


Remember!

God

Nothing

Something

Atoms

(Chemical bonds, Crystals)

Chemical elements


Rocks are aggregates of one or more mineral.

The nature and properties of a rock are determined by the:

-minerals in it;-minerals in it;

-manner in which the minerals are arranged relative to

each other (the texture of the rock);

-weathering (affect the engineering properties of a rock).

According to their manner of formation, rocks are of

three main types:

-igneous rocks;

-sedimentary rocks;

-metamorphic rocks


Source: InternetGranite Sandstone Gneiss


Igneous rocks are formed from magma, which has:

-originated well below the surface;

-ascended towards the surface;

-crystallised as solid rock either on the surface or deep

within the Earth’s crust as its temperature fell.

Source: Internet


Each mineral starts to crystallise at a particular

temperature and continues to form throughout a limited

temperature range as the magma cools.

Since the crystals formed early have a higher specific

gravity than the remaining liquid of the magma, theygravity than the remaining liquid of the magma, they

settle downwards.

As time progresses, different minerals crystallise from the

magma.

This process is named magma differentiation.


Source: Geology for Civil Engineers – A.C.McLean, C.D. Gribble


Source: Geology for Civil Engineers – A.C.McLean, C.D. Gribble


acid basic

Quartz no Quartz

Orthoclase

Oligoclase

Muscovite Biotite Biotite Biotite

Hornblende Hornblende Hornblende

Augite Augite Augite

intermediate

little or no Quartz

Orthoclase Plagioclase

commenest

mineral

Plagioclase

Augite Augite Augite

Olivine

volcanic

(extrusive)Rhyolite

Quartz

Porphyries

Orthoclase

Porphyries

Plagioclase

Porphyries

Trachyte Andesite Basalt

Dolerite

Gabbro

hypabyssal

plutonic

(intrusive)Granite Syenite Diorite


Texture of igneous rocks – crystalline texture

Medium-grained rock

Source: Internet

Coarse-grained rock

Fine-grained rock


Texture of igneous rocks – glassy texture

Source: Internet


Texture of igneous rocks – porphyfiritic texture

Source: Internet

Extrusive rockIntrusive rocks


Texture of igneous rocks – vesicular and amigdaloidal texture

Source: Internet


Texture of igneous rocks – pegmatitic texture

Source: Internet

Theme 6.

Sedimentary rocks

6.1. Sedimentary rocks formation

6.2. Classification of sedimentary rocks

6.3. Features of sedimentary rocks


Sedimentary rocks are formed from the solid debris

and the dissolved mineral matter produced by:

-the mechanical and chemical weathering of pre-

existing rocks,

-or from the skeletal material of dead plants and-or from the skeletal material of dead plants and

animals.


The processes involved in the disintegration of rocks

by weathering and erosion, and the transport of

these products to the place where they are

deposited, are all very important.

The deposits of sedimentary rocks recently formed

are the natural material encountered and dealt with

in nearly every shallow excavation.in nearly every shallow excavation.

Source: Internet

Sedimentary rocks were once sediments, and so they

are records of the conditions at Earth's surface when

and where the sediments were deposited.


The nature of a sedimentary

rock, and its position in a

scheme of rockscheme of rock

classification, are partly

dependent on these original

conditions of transport and

deposition.

Source: Understanding Earth – J.Grotzinger,

T.H. Jordan, F. Press, R. Siever

According to the type of environment in which it

accumulated there are:

-continental deposit;

-intermediate deposit;

-marine deposit.


-marine deposit.

Source: Internet

Sedimentary rocks also reveal

former plate tectonic events

and processes by their

presence within or adjacent

to volcanic arcs, rift valleys,

or collisional mountains.


or collisional mountains.


Sediments, and the sedimentary rocks formed from

them, are produced by the surface processes of the

rock cycle.

They form after rocks have been moved from Earth's

interior to its surface by mountain building and

before they are returned to Earth's interior by


before they are returned to Earth's interior by

subduction.

These processes involve a source area, where the

sediment particles are created, and a sink area where

they are deposited in layers.

6.1. Sedimentary rocks formation –

the sedimentary stages of the rock cycle


Weathering is the general process by which rocks are

broken down at Earth's surface to produce sediment

particles.

There are two types of weathering:

-Physical weathering ;


-Physical weathering ;

-Chemical weathering .

Source: Internet

Erosion mobilizes the particles produced by

weathering, most commonly by rainwater running

downhill.


Source: Internet

Transportation occurs when currents of wind and

water and the moving ice of glaciers transport

particles to new locations—sediment sinks—downhill

or downstream.


Source: Internet

Deposition (sedimentation) occurs when sedimentary

particles settle out as winds die down, water currents

slow, or glacier edges melt.

These particles form layers of sediment on land or

under the sea in sedimentary basins.


Source: Internet

Diagenesis refers to the physical and chemical

changes (pressure, heat, and chemical reactions) by

which sediments buried within sedimentary basins

are lithified, or converted into sedimentary rocks.


Source: Internet


The four major groups of sedimentary rocks are:

-detrital (clastic) sedimentary rocks (which are formed from

minerals or rock fragments derived from the breakdown of

preexisting rocks);

-chemical sedimentary rocks (which are formed from the-chemical sedimentary rocks (which are formed from the

precipitation of salts dissolved in water);

-organic sedimentary rocks (which are formed from the skeletal

remains of plants and animals);

-limestones and dolomites (which are sedimentary rocks

consisting of more than 50% carbonate, and can include chemical,

clastic and biological material).


Source: Internet


Source: Internet


Source: Internet


Source: Internet


Source: Internet


From an engineering perspective soils generally refer to

sedimentary materials that have not been cemented and sedimentary materials that have not been cemented and

have not been subjected to high compressive stresses.


Coarse-grained soils

These include sands, gravels and larger particles.

For these soils the grains are well defined and may be seen For these soils the grains are well defined and may be seen

by the naked eye.

The individual particles may vary from perfectly round to

highly angular reflecting their geological origins.


Symbol /Type of soil Particle size (mm)

Very Coarse-grained

soils

LBo (large boulders) > 630

Bo (boulders) 200 ÷ 630

Co (cobbles) 63 ÷ 200

Gr (gravel) 2.0 ÷ 63

CGr (coarse gravel) 20 ÷ 63

MGr (medium gravel) 6.3 ÷ 20

Coarse-grained soils

MGr (medium gravel) 6.3 ÷ 20

FGr (fine gravel) 2.0 ÷ 6.3

Sa (sand) 0.063 ÷ 2.0

CSa (coarse sand) 0.63 ÷ 2.0

MSa (medium sand) 0.2 ÷ 0.63

FSa (fine sand) 0.063 ÷ 0.2

SR EN ISO 14688-1:2004



Fine-grained soils

These include the silts and clays and have particles smaller

than 63 µm.

Silts These can be visually differentiated from clays

because they exhibit the property of dilatancy. If a

moist sample is shaken in the hand water will appear on

the surface. If the sample is then squeezed in the fingers

the water will disappear. Their gritty feel can also identify

silts.


Fine-grained soils

These include the silts and clays and have particles smaller

than 63 µm.

Clays Clays exhibit plasticity, they may be readily

remoulded when moist, and if left to dry can attain high

strengths


Symbol /Type of soil Particle size (mm)

Fine-grained soils

Si (silt) 0.002 ÷ 0.063

CSi (coarse silt) 0.02 ÷ 0.063

MSi (medium silt) 0.0063 ÷ 0.02Fine-grained soils MSi (medium silt) 0.0063 ÷ 0.02

FSi (fine silt) 0.002 ÷ 0.0063

Cl (clay) ≤≤≤≤ 0.002

SR EN ISO 14688-1:2004



The composition of a sedimentary rock will depend on the

source from which the waste material came, on the

resistance, chemical and mechanical, of each component

during transport, and on the distance travelled.

The main constituents of detrital sedimentary rocks are

fragments from pre-existing rocks and minerals. These mayfragments from pre-existing rocks and minerals. These may

be fresh and unaltered, or may be alteration products of

weathering (clay minerals). Quartz is the most common

mineral.

Some minerals in sedimentary rocks may be formed in the

area of deposition: minerals precipitated from solution to

form the chemical sedimentary rocks (calcite, dolomite and

siderite, gypsum and anhydrite, chlorides, silica).


The texture of sedimentary rocks is dependent on the

sizes, shapes and arrangement of these fragments.

The size of grains is an important textural feature.

The degree of roundness of grains is related to the amountThe degree of roundness of grains is related to the amount

of abrasion suffered during transport, and hence to

distance travelled from their source before deposition.

Documents

Theme 5. Igneous rocks - Jurnalul lui Ştefan · Theme 5. Igneous rocks 5.1. Igneous rocks and plate tectonics 5.2. Igneous structures and forms 5.3. ... T.H. Jordan, F. Press, R